Methods for interconverting olefins in an olefin-rich hydrocarbon stream include contacting the olefin-rich hydrocarbon stream with a catalyst system in an olefin interconversion unit to produce an interconverted effluent comprising ethylene and propylene. The contacting may be conducted at a reaction temperature from 450° C. to 750° C., a reaction pressure from 1 bar to 5 bar, and a residence time from 0.5 seconds to 1000 seconds. The catalyst system includes a framework-substituted beta zeolite. The framework-substituted beta zeolite has a *BEA aluminosilicate framework that has been modified by substituting a portion of framework aluminum atoms of the *BEA aluminosilicate framework with beta-zeolite Al-substitution atoms independently selected from the group consisting of titanium atoms, zirconium atoms, hafnium atoms, and combinations thereof.